Optical package with alignment means and method of assembling an optical package

ABSTRACT

An optical package is provided having a diode mounted to a substrate enclosed by a housing which includes a bore for receiving an optical waveguide and a focusing element adjacent the bore. The bore and focusing element are aligned along a common optical axis. An alignment means is associated with the housing for aligning the substrate along the optical axis.

This application is a continuation-in-part of U.S. Ser. No. 08/588,445,filed on Jan. 18, 1996.

BACKGROUND OF THE INVENTION

This invention pertains generally to optical transceivers and, inparticular, to an optical device package for an optical transceiver.

Optical transceivers are known in the art and include active opticaldevices or diode packages. Common diode packages include LED packagessuch as a TO46 package or a laser diode package such as RLD-85PC diodepackage by Rohm, Incorporated. These diode packages or TO cans typicallyinclude a metallic housing having a laser diode or LED for transmittingdata and a photo diode for performing power-monitoring, metal contactleads exiting from the diodes for connection to a power source and acover glass opposed to the diode, through which the energy istransmitted. The TO can is hermetically sealed. The hermetic sealing ofthe TO can is a time-consuming and expensive process which adds to theoverall expense of the LED or laser package. As well, the commonly knownTO cans do not have the emission area of the diode aligned within the TOcan in a consistently centered orientation. Thus, placement of the TOcan in a uniform position does not provide for alignment of the diode toan optical connector and maximum power transmission is not achieved.Thus, alignment of the TO package becomes a time-consuming and expensiveprocess.

Commonly known housings for optical transceivers require complexmechanical means in order to align the diode package, the lens, the boreand the optical waveguide ferrule. Mechanical means, such as a screw iscommonly used to actively align the TO can within the housing. Further,a molded plastic housing is often used having precision molded cavitiesspecifically sized for receiving a diode package, another cavityspecifically sized for receiving a lens and another cavity specificallysized for receiving an optical waveguide ferrule. Such an opticaltransceiver housing is often rendered ineffective in production due tovariations in the alignment of the LED or laser relative to the TO can.

In view of the above, it is an object of the present invention toprovide an optical device package which is quickly and inexpensivelymanufactured.

It is a further object of the present invention to provide an opticaldevice package which may be easily aligned with an optical transceiverhousing.

It is another object of the present invention to provide an opticalpackage having a single optical axis.

SUMMARY OF THE INVENTION

A principal object of this invention is to provide an optical packagecomprising a housing including a bore for receiving an optical waveguideand a focusing element adjacent the bore, the bore and the focusingelement being aligned along a common optical axis, a diode mounted to asubstrate adjacent the focusing element and an alignment meansassociated with the housing for aligning the substrate along the opticalaxis. The alignment means may include a trace located in a predeterminedposition on the substrate to which the housing is mounted. The alignmentmeans may include a groove located in a predetermined position on thesubstrate to which the housing is mounted. The housing may include anouter sleeve defining the bore for receiving an optical waveguide and aninner sleeve for receiving the focusing element. The inner sleeve mayinclude a lens support means for mounting the focusing element. Thefocusing element may be mounted in a lens support means. The lenssupport means may include a plastic washer having a bore of a diameterless than the diameter of the focusing element. The focusing element maybe a ball lens. The groove may be formed between conductive tracesadhered to the substrate. The groove may be integrally molded with thesubstrate. The bore may have a diameter of approximately 0.0984 inchesor greater. The height of the inner sleeve may be less than the heightof the outer sleeve. The inner sleeve may be partially filled with anoptical filler composition. The alignment means may include a precisionformed aperture in the housing for receiving the substrate. Thesubstrate may be a precision formed material having a predetermined sizeand the diode mounted thereto in a predetermined orientation on thesubstrate. The focusing element may be integrally molded with thehousing. The housing and the focusing element may be formed of atransmissive material allowing for the transmission of wavelengths from780-1350 nanometers.

In an embodiment, an optical package is provided comprising a substratehaving a diode mounted thereto and a groove formed in the substratesurrounding the diode, an inner sleeve mounted within the groove havinga lens therein and an outer sleeve mounted to the substrate surroundingthe inner sleeve for receiving an optical ferrule. The groove may beformed between conductive traces adhered to the substrate. The groovemay be integrally molded with the substrate. The inner sleeve mayinclude a tab protruding within the sleeve to provide support to thelens. The inner sleeve may be formed of stainless steel, brass, nickelsilver or ARCAP®. The outer sleeve may have a cylindrical shape andinclude a bore having an inner diameter of 0.0984 inches or greater. Theheight of the inner sleeve may be less than the height of the outersleeve. The diode may be a surface emitting diode. The diode may be anLED. The diode may be a vertical cavity surface emitting laser (VCSEL).The diode may be a photodiode. The inner sleeve may be partially filledwith an optical filler composition. The optical filler composition maybe an epoxy or a silicone composition. The optical filler compositionmay form a meniscus at the base of the lens to provide retention of thelens. The tabs of the inner sleeve may be formed from portions of theinner sleeve wall which are punched from the wall and protrude withinthe interior of the inner sleeve. The optical package may include asingle optical axis wherein the diode has an emission point providing anemission axis upon which the lens and the ferrule are aligned.

In an embodiment, an optical package is provided comprising a substratehaving an outer trace forming a circle and a pair of circular concentricinner traces formed within the outer trace and the pair of concentricinner traces defining a groove therebetween, an inner cylindrical sleevemounted within the groove including a tab punched from the sidewall ofthe inner sleeve protruding toward the center of the cylindrical innersleeve, a surface emitting diode and lens mounted within the innersleeve and an outer cylindrical sleeve mounted on the outer tracedefining an inner bore having a diameter of 0.0984 inches or greater andhaving a height greater than the inner sleeve. The inner traces may beformed from conductive copper traces. The diode may be mounted to thesubstrate. The lens may be a ball lens supported by the tab of the innersleeve.

In an embodiment, an optical package is provided comprising a housingincluding a bore for receiving an optical waveguide, a focusing elementadjacent the bore and a precision formed aperture for receiving asubstrate, the bore, the focusing element and the aperture being alignedalong a common optical axis and a diode mounted to the substrate. Thesubstrate may be a precision formed material having a predetermined sizeand the diode mounted thereto in a predetermined orientation on thesubstrate. The substrate may be formed of a silicon material. Thefocusing element may be integrally molded with the housing.

A method of assembling an optical package is provided including thesteps of forming a housing having a bore and a focusing element adjacentthe bore, the focusing element and the bore aligned along a commonoptical axis, mounting a diode to a substrate in a predeterminedposition and mounting the substrate to the housing so that the diode iscentered on the optical axis. The method further including the steps offorming an alignment means on the substrate or the housing and mountingthe substrate to the housing via the alignment means. The method furtherincluding the steps of forming the alignment means of a precisionaperture in the housing and receiving a precision formed substrate inthe aperture.

The method further including the steps of forming a groove on asubstrate surrounding a central point, mounting the diode at the centralpoint of the substrate, mounting an inner sleeve within the groove,securing the inner sleeve to the substrate, mounting the focusingelement within the inner sleeve, placing an outer sleeve on thesubstrate surrounding the inner sleeve, aligning the outer sleeve alongthe optical axis and securing the outer sleeve to the substrate. Themethod of assembling the optical package may include the step ofinjecting an optical filler composition into the inner sleeve after thelens is inserted therein. The method of assembling the optical packagewherein the outer sleeve is mounted on an outer conductive trace adheredto the substrate and the outer sleeve is secured thereto via solder. Themethod of assembling an optical package wherein the outer sleeve may beintegrally molded with the lens and inner sleeve. The method ofassembling an optical package wherein the outer sleeve is activelyaligned by inserting a ferrule of an optical waveguide attached to apower meter and to the bore of the outer sleeve, adjusting the outersleeve laterally until a desired power level is achieved and securingthe outer sleeve to the substrate.

As noted, an optical package can be made of molded plastic havingprecision molded cavities formed therein. Additional embodiments takeadvantage of the many special properties of a plastic housing, providingadditional alternate mechanisms for aligning a bore, a focusing element,and a substrate having an optical diode mounted thereon. In anembodiment, the housing is formed with a first bore for receiving anoptical waveguide in the form of a fiber optic connector ferrulesurrounding an optical fiber. A second bore, or more generally a basecavity, is formed in the base of the housing opposite the first bore.The base cavity is configured to receive a focusing element and anoptical element, such as a VCSEL, LED, or photodiode. A smaller internalcavity is formed at the end of the base cavity, and acts as a supportmeans for the focusing element. A small through hole communicatesbetween the focusing element support cavity and the first bore, allowingoptical radiation to pass from the focusing element to an opticalwaveguide inserted into the first bore. Mounting posts extend from thebase of the housing, circumferentially spaced around the base cavity.The optical element is mounted to a separate substrate having alignmentholes formed therein. The alignment holes are positioned to receive themounting posts extending from the base of the housing, and are formedhaving a larger diameter than the posts such that the substrate can bemaneuvered relative to the housing to facilitate alignment of thevarious optical components. Alignment is performed actively, and whenthe maximum amount of optical radiation is coupled to the opticalwaveguide, the posts are bonded to the substrate to hold the housing inplace and maintain proper alignment.

Optional bonding methods include reflowing the plastic posts using a CO₂laser, infrared heat source, hot air, or some other means of heating andmelting the plastic posts. Using this technique the mounting posts aremelted and the molten plastic reflows into the alignment holes, fillingthe spaces between the posts and the substrate. After completely fillingthe alignment holes, the excess plastic from the melted posts forms ameniscus or mushroom shaped dome of material over each alignment hole.Upon cooling, the plastic hardens to form a secure bond between thehousing and the substrate. A similar method for adhering the housing tothe substrate involves heating the plastic posts, but rather than fullymelting and reflowing the posts, either a rivet forming tool or acompressive blast of hot air is used to compress the posts into theproper mushroom shaped dome necessary to secure the substrate to thehousing. A third method for bonding the housing to the substrateinvolves hot melting an epoxy into the alignment holes and allowing theepoxy to bond the two pieces together. Finally, a fourth method involvesforming the substrate itself out of a plastic material similar to thatused for the housing, and laser welding the two pieces together. Whilethe methods disclosed herein are preferred, it should be clear to thoseskilled in the art that other bonding methods may be employed withoutdeviating from the novel aspects of the present invention.

In another embodiment incorporating a plastic housing, the plastichousing is identical to that described previously, except the mountingposts are omitted. In their place, a circular metal insert is insertedinto the base cavity of the housing. The metal insert is formed with anannular flange which engages the base of the housing to provide apositive stop against excessive insertion of the insert into thehousing. Surface features such as a knurled finish, or threads, or someother friction enhancing feature, are formed on the outer surface of theinsert so that upon insertion into the housing, the insert frictionallyengages the side walls of the housing. The optical device is mounted ona substrate which is either partially or entirely formed of metal.Minimally, the edges of the substrate are metallized to facilitatebonding the substrate to the metal insert. The substrate is placed overthe annular flange and the optical components actively aligned. Uponproper alignment of the optical components, the metallized edges of thesubstrate are bonded to the annular flange of the metal insert by laserwelding, soldering, or other known techniques for bonding metalcomponents.

In an embodiment, the lens cavity is formed immediately adjacent theoptics cavity, and retaining features are molded into the lens cavityaround the opening joining the lens cavity to the optics cavity. Theretaining features act to hold the focusing element within the lenscavity. The retaining features are slightly compressible so that thefocusing element can be press fit into the cavity past the retainingfeatures. When the focusing element is fully inserted past the retainingfeatures, the retaining features expand to their natural extent, therebycapturing the focusing element within the lens cavity.

In another, similar embodiment, the lens cavity is formed immediatelyadjacent the ferrule receiving bore. The focusing element is insertableinto the lens cavity through the ferrule receiving bore. Compressibleretaining features are molded into the lens cavity around the openingjoining the lens cavity to the ferrule receiving bore.

In a further embodiment, a plastic housing provides an improvedmechanism for aligning the mating optical waveguide with the plasticoptical package. A split bore feature is incorporated with a firstoptical waveguide receiving bore. The split bore embodiment contemplatesat least one narrow slot formed in the optical waveguide receiving bore,extending from the receiving end of the bore toward the base of the borenear the point where a focusing element is mounted. The slot or slotsallow the walls of the housing to flex as the waveguide is inserted intothe bore. Precision alignment of the waveguide is only necessary at thebase end of the bore adjacent the focusing element. The flexibility ofthe bore sidewalls diminishes toward the end of the slots. Thus, as anoptical waveguide is inserted into the bore, the increasing rigidity ofthe sidewalls gradually forces the waveguide to the precision alignmentposition at the base of the bore. This arrangement has the advantages ofsimplifying the mating procedure of the waveguide to the housing, andreducing the area of precision molding necessary to properly align thewaveguide, thereby reducing the cost of molding the plastic housing.

These and other features of the invention are set forth below in thefollowing detailed description of the presently preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation cut-away view of the present invention;

FIG. 2 is a perspective view of the present invention partially cutaway;

FIG. 3 is a side elevation cut-away view of an alternate embodiment ofthe present invention;

FIG. 4 is a side elevation cut-away view of another alternate embodimentof the present invention; and

FIG. 5 is a side elevation cut-away view of a further alternativeembodiment of the present invention.

FIG. 6A is a side elevation cut-away view of an additional alternativeembodiment of the present invention;

FIG. 6B is an end view of the embodiment shown in FIG. 6A showing asubstrate member covering the base of the optical housing, with housingmounting posts extending through alignment holes formed in thesubstrate;

FIG. 6C is a section view of the plastic housing and substrate of FIG.6A after the mounting posts have been reflowed to bond the substrate tothe housing;

FIG. 7 is a side elevation cut-away view of yet another alternativeembodiment of the present invention;

FIG. 8A is a cross section of a plastic optics package showing a balllens captured within a lens cavity with retaining features, the lenscavity opening into the optics cavity;

FIG. 8B is an end view of the plastic optics package of FIG. 8A showingretaining features extending into the lens cavity;

FIG. 9 is a cross section of a plastic optics package showing a balllens captured within a lens cavity with retaining features, the lenscavity opening into the ferrule receiving bore;

FIG. 10 shows a split bore feature formed in an optical waveguidereceiving bore; and

FIG. 10A shows a second embodiment of a split bore feature.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention, as shown in FIG. 1, relates to an optical packagehousing 10 comprising a substrate 20 having an alignment means such astraces 30 adhered thereto. Mounted to the substrate 20 is inner sleeve40 and outer sleeve 50. Mounted within the inner sleeve 40 is ball lens60 and optical device or diode 70. Received within the outer sleeve 50is optical waveguide ferrule 80 including optical fiber 85. The presentinvention may be better understood by a description of a preferredembodiment of assembling the optical package housing 10. The substrate20, for example, FR4, has traces 30, such as conductive four ouncecopper traces adhered thereto. For example, a subtractive etchingprocess or an additive process such as vacuum deposition may be used topattern the substrate 20. The conductive traces 30 are adhered in apredetermined orientation providing for an outer trace 31, a sleevegroove 33 and also forming through-holes 35. The through-holes 35provide retention points for the conductive traces 30 to avoiddelamination of the conductive traces 30 from the substrate 20 whensubjected to mechanical stress. In an alternate embodiment,through-holes 35 may provide an access point for injecting an opticalfiller composition such as an epoxy within the cavity of the innersleeve 40 to provide for index matching or chip passivation. In analternative embodiment, the substrate 20 may be a polymer material andthe conductive traces 30 may be a conductive ink adhered thereto or thegroove 33 may be integrally molded of the polymer material. The outertrace 31 and sleeve groove 33 provide for a means of aligning theoptical package 10. The outer trace 31 and sleeve groove 33 are circularin order to receive the cylindrical outer sleeve 50 and cylindricalinner sleeve 40, respectively. The diode 70 is mounted to the conductivetrace 37. In a preferred embodiment, a surface emitting LED is used.However, a laser or photodiode may be incorporated as well. The LED 70receives its power from a pin inserted in through-hole 35 or a circuittrace on the backside of substrate 20 which is attached via a wire bond72 to the diode 70. Also mounted to the substrate are the electronics tooperate the optical device, for example, a driver circuit for atransmitter or an amplification and decision circuit for a receiver andconnected to the LED or pin diode via conductive trace 37. Also, mountedto the substrate may be a power feedback means.

The inner sleeve 40 is assembled by forming lens support means, or tabs41,42 from the sidewalls of the inner sleeve 40. In a preferredembodiment, the inner sleeve 40 is formed of a metallic material such asstainless steel, brass, nickel silver, or ARCAP®. The inner sleeve 40 isthen mounted within sleeve groove 33 on the substrate 20. The groove 33acts as an alignment means for the inner sleeve 40. The inner sleeve 40is attached within the groove 33 by solder 46. A focusing element, suchas a ball lens 60 is then placed within the sleeve 40 so that it restson the distal ends of the tabs 41,42. The area of the inner sleeve 40below the ball lens 60 is filled with an optical filler composition suchas epoxy. The epoxy provides retention and support for the ball lens 60beyond the tabs 41,42 and also protects the LED 70. The fillercomposition may also provide for an optical attenuator having apredetermined refractive index such as by using filled silicone orepoxy. Therefore, it may be understood that the ball lens 60 ismaintained in its lateral and axially orientation within the innersleeve 40 by the tabs 41,42 of the sleeve 40. In addition, the sleeve 40may have an inner diameter equal to the outer diameter of the ball lens60 so that a snug fit is achieved when the ball is inserted within thesleeve 40 so that it is supported at its bottom by the tabs 41,42 and atits equator by the sides of the sleeve 40. While a ball lens is apreferred light condensing element, other lenses may also be insertedwithin the sleeve 40.

The outer sleeve 50 is then mounted to the substrate 20. Generally, theouter sleeve 50 has a bore 51 having an inner diameter slightly greaterthan the diameter of a standard ferrule of 0.0984 inches. A ferrule 80is then inserted within the bore of the outer sleeve 50. The opticalwaveguide, or ferrule 80 is inserted until it abuts the distal end 48 ofthe inner sleeve 40. The distal end 48 of the inner sleeve 40 prohibitsthe insertion of the ferrule any further. While the inner sleeve 40 isgenerally rigid, the ferrule 80 is generally mounted within a fiberoptic connector having a spring to provide for axial compression of theferrule 80 so that upon abutment with the distal end 48 of the innersleeve 40, there is some compression provided to avoid damaging the endface of the ferrule 80. The distal end 48 of the inner sleeve 40 isformed as straight as possible so that abutment with the ferrule 80 actsto enclose the inner chamber of the inner sleeve 40 so that there arelittle or no gaps between the ferrule 80 and the distal end 48 of theinner sleeve 40. In any event, the ball lens 60 will focus the majorityof the light emitted from the diode 70 toward the optical fiber 85within the ferrule 80.

The optical package 10 is then actively aligned. The ferrule 80 isattached to a power meter and the outer sleeve 50 is moved laterallyalong the substrate 20 in order to find the optimum alignment position.Upon finding the optimal alignment position where the photons emittedfrom the emission point 75 of the LED or laser provide the highest powerupon transmission through the optical fiber 85 of the ferrule 80, theouter sleeve 50 is secured in place. The outer sleeve 50 is secured tothe outer trace 31 by solder 56,57 adhered along the bottom edge of theouter sleeve 50. Any standard means of applying solder may be used suchas a solder gun or via solder pads adhered to the outer trace 31 or thesubstrate 20 and being exposed to heat such as infrared or hot air. Theouter trace 31 acts as an alignment means for the outer sleeve 50.Therefore, it may be understood that an optical package 10 is providedwhich eliminates the need for a preassembled TO can and provides for aneasily and inexpensively assembled and aligned package. In a preferredembodiment, the package has a single optical axis. As shown in FIG. 1,the emission axis from the emission point 75 of the optical element 70is the same axis upon which the lens 60 and optical fiber 85 arealigned. This arrangement allows for the simple construction of thecoaxial sleeves 40,50 of the present invention.

Turning to FIG. 2, a perspective view of the invention is shown. Thesubstrate 20 and traces 30 are shown in a complete view while the outersleeve 50 and the inner sleeve 40 are shown partially cut away so thatthe present invention may be more easily viewed. Adhered to thesubstrate 20 is outer trace 31, and inner traces 32 and 34 which definesleeve groove 33. Also adhered to the substrate 20 is conductive pad 37.The conductive pad 37 has mounted thereto diode 70. In the embodimentshown in FIG. 2, the diode 70 is a vertical cavity surface emittinglaser (VCSEL). The diode 70 receives power from wirebonds 72.

The inner sleeve 40 is mounted within sleeve groove 33 and securedwithin the groove 33 and to the traces 32,34 by a chemical bonding agent46 such as epoxy or solder. Tabs 41,42 are punched out of the sides ofthe inner sleeve 40 so that they protrude generally perpendicular to theinner sleeve walls 40 toward the interior of the inner sleeve 40. Theinner sleeve 40, in a preferred embodiment, forms a hollow cylinderexcept for the tabs 41,42 protruding toward the center of the cylinder.In a preferred embodiment, four tabs protrude into the cylinder in orderto support the ball lens 60 therein. The ball lens 60 is mounted withinthe inner sleeve 40 and is supported by tabs 41,42. An optical fillercomposition 25 is injected into the bottom of the inner sleeve 40 inorder to seal the diode 70 and support the ball lens 60 and secure it ina centered position along the optical axis above the emission point 75of the diode 70. An optical filler composition such as an epoxy oroptical silicone may be used. The filler composition 25 forms a meniscus26 below the tabs 41,42 and above the base 61 of the ball lens 60. Inaccordance with the present invention, it can be understood that themounting of the inner sleeve 40 as discussed above, is quickly andeasily assembled and overcomes the need for an expensive component suchas a TO-46 diode can. The mounting of the diode 70 to the substrate 20and the inner sleeve 40 require alignment within approximately 0.003inches of the optical axis of the optical package housing 10.

The precision alignment is performed by active alignment of the outersleeve 50. The outer sleeve 50 is a cylindrical shell mounted on thecircular outer trace 31. In a preferred embodiment, the outer sleeve 50may be a solderable metallic material such as nickel silver, brass orARCAP®. In an alternate embodiment, the outer sleeve 50 may be made of apolymer material such as Valox and may be molded integrally with thelens and inner sleeve which may also be a polymer material. The outersleeve 50 includes a precision aligned bore 51 which may be polished.The bore 51 includes a diameter of approximately 0.0984 inches orgreater to provide a low insertion force fit around a ferrule of anoptical waveguide. Other ferrule diameters may also be accommodated bythe bore 51 to allow for insertion of ferrules having a diameter of lessthan or greater than 0.0984 inches. Prior to securement of the outersleeve 50 to the substrate 20, a ferrule is inserted within the bore 51until it reaches the top edge 48 of the sleeve 40. The edge 48 acts as astop-abutment to the ferrule.

The ferrule inserted within the bore 51 will be attached to an opticalwaveguide which is attached to a power meter in order to measure thepower level being transmitted through the optical waveguide. The ferrulesleeve 50 is moved laterally on the substrate 20 which simultaneouslymoves the ferrule inserted within the bore 51 of the outer sleeve 50.The optical fiber position is adjusted along a transverse axis to alight beam or emission axis of the diode 70. Upon locating the outersleeve 50 in a position achieving a satisfactory power level, the outersleeve 50 is then secured to the substrate using solder or a chemicalbonding composition. For example, an epoxy or solder 56,57 may be used.According to the above description, it may be understood that an opticaltransceiver apparatus may be easily, quickly and inexpensivelymanufactured. Such an apparatus may provide for transmission of lightwaves with a coupling efficiency in excess of 25% at an operatingtemperature between -40° and +85° Celsius.

Turning to FIG. 3, an alternate embodiment of the present invention isshown having optical package housing 110 having a bore 151 for receivingferrule 180. Adjacent the bore 151 is lower aperture 155. Mounted withinthe lower aperture 155 is lens support means 141. In this alternateembodiment, the lens support means 141 may be a washer made of a polymermaterial having an inner bore 143 having a length greater than thediameter of ball lens 160. In a preferred method of assembling thealternate embodiment shown in FIG. 3, the washer 141 is inserted withinthe aperture 155 so that it is adjacent the bore 151. A focusing elementsuch as a ball lens 160 is inserted within the inner bore 143 of thewasher 141. The inner bore 143 has a diameter slightly less than thediameter ball lens 161 so that the sidewalls 145 of the washer 141expand upon insertion of the ball lens 160 therein. Therefore, it ispreferred that a flexible polymer material such as SANTOPRENE™ (AdvancedElastomer Systems, L.P.) be used. The ball lens 160 may be inserted inthe inner bore 143 of the washer 141 using an insertion tool. The washer141 may be secured within the aperture 155 via chemical bonding meanssuch as by epoxy. In addition, the force of the ball lens deforming thesidewalls 145 also causes the washer 141 to deform and frictionally abutthe walls of the aperture 155 and aids in securing the washer 141 inposition. The aperture 155 and the bore 151 are precision machined froma solderable material such as brass, nickel silver, or ARCAP® so that anoptical waveguide 180 inserted within the bore 151 will be aligned alongan optical axis which bisects the focusing element 160 mounted withinthe lens support means 141.

The optical package housing 110 is then mounted to a substrate 120similar to that discussed above for the outer sleeve 50 as shown inFIGS. 1 and 2. The housing 110 is placed onto the substrate 120 so thatthe aperture 155 encloses the diode 170. The diode may include, but isnot limited to, an LED, a VCSEL, a laser diode or a photodiode. Theoptical package is actively aligned by powering up the diode 170 andattaching the optical waveguide 180 to a power meter and moving thehousing 110 laterally along the substrate 120 until an optimum readingis achieved. The housing 110 is preferably formed of a solderablematerial such as ARCAP® and the housing is soldered at solder points156,157 to the alignment means or traces 131 of the substrate 120. Theembodiment of FIG. 3 is an improvement over the embodiment of FIGS. 1and 2 in that the housing 110 is a single unit which has the bore 151and the lower aperture 155 formed of a single member. Therefore, it isnot necessary to align both an outer and inner sleeve on a substrate.

A further alternate embodiment of the present invention may beunderstood with reference to FIG. 3 which provides for passivealignment. The substrate 120 may include along its upper surface agroove such as that shown in FIGS. 1 and 2, however, being precisionformed to receive a protruding member from the housing 110. Thesubstrate 120 may be precision formed such as by molding of a polymersubstrate and the diode 170 may be precision aligned to the substrate.Upon mounting of the housing 110 to the substrate 120, the diode 170will be passively precision aligned along a common single optical axiswith the focusing element 160 and the bore 151. The focusing element 160and the lens support means 141 may be both integrally molded with thehousing 110, such as disclosed for FIGS. 4 and 5.

Turning to FIG. 4, another alternate embodiment of the present inventionis shown having a housing 210 having a bore 251 for receiving an opticalwaveguide 280. Adjacent the bore 251 is a focusing element 260 andadjacent the focusing element 260 is an alignment means or precisionformed lower aperture 255. In this alternate embodiment, the housing 210is preferably formed of a transmissive material such as Ultem® and thefocusing element 261 is integrally molded with the rest of the housing210. The housing 210 is made of a material which allows for thetransmission of lightwaves in the range of 780-1350 nanometers. Thefocusing element 261 includes a light refracting surface 263 and 264.Mounted within the aperture 255 is a substrate 220 which has mountedthereto a diode 270. The diode may include, but is not limited to, anLED, a VCSEL, a laser diode or photodiode. The substrate 220 isprecision formed so that its dimensions are precisely formed to apredetermined size. The substrate 220 is preferably a silicon materialwhich is anisotropically etched and cleaved to a predetermined size. Thewalls of the aperture 255 are also precision formed so that uponinsertion of the substrate 220 within the aperture 255, the diode 270which is also precision aligned on the substrate 220 will be alignedalong an optical axis upon which the focusing element 261 and the bore251 are centered. The aperture 255 of the housing 210 may be precisionformed by any known methods, for example, using precision moldingtechniques including, injection molding, casting or precision grindingmethods. The diode 270 is mounted on the silicon substrate using knownmethods of alignment, such as by infrared alignment means. Thisembodiment allows for passive alignment of the optical package. Thesubstrate 220 is inserted within the aperture 255 so that it mounts in apredetermined, centered position. The emission point of the diode iscentered on the optical axis so that the light waves of the diode strikerefracting surface 263 of the focusing element 261. The light waves arethen focused and transmitted from the refracting surface 264 of thefocusing element 261 into the optical fiber 285 of the optical waveguide280.

The substrate 220 may also have electronics to operate the opticaldevice, including a driver circuit, an amplification and decisioncircuit and a power feedback means. The substrate 220 may beelectrically connected via contacts 272 which may be mounted within thehousing material 210 and have exposed portions adjacent the substrate220 and the substrate may be soldered thereto. The substrate 220 may besecured within the aperture 255 via means such as chemical bonding, forexample use of an epoxy composition. The embodiment shown in FIG. 4discloses the diode 270 mounted on the substrate 220 adjacent thefocusing element 261. Use of an epoxy or silicone compound "passivates"the LED or laser by creating a barrier to moisture and/or othercorrosive agents.

Turning to FIG. 5, a further alternate embodiment is shown having thediode 370 mounted as a "flip chip" or on the surface of the substrate320 opposite the surface which is adjacent the focusing element 360 sothat the emission point is abutting the substrate and transmitstherethrough. The diode may include, but is not limited to, an LED, aVCSEL, a laser diode or a photodiode. In such an orientation, thesubstrate 320 may have its electronics connected via flexible circuitmember 372 to external components. In such an embodiment, the substrate320 is preferably formed of a material which is optically transmissiveand allows for the transmission of lightwaves of up to 780-1350nanometers such as silicon or transparent glass. The embodiment of FIG.5 also allows for passive alignment similar to the embodiment of FIG. 4in that the substrate is positioned within aperture 355 so that theprepositioned diode 370 is aligned on the optical axis along with thefocusing element 361 and the bore 351.

Additional embodiments are shown in FIGS. 6 and 7 incorporating a singlepiece plastic housing. Turning to FIG. 6, a generally cylindrical shapedhousing 400 is shown in cross section taken along the axial centerlineof the cylinder. The housing includes a first bore 402 for receiving anoptical waveguide 404 enclosed in an alignment ferrule 406. As with theprevious embodiments, first bore 402 has a diameter only slightly largerthan a standard ferrule diameter of 0.0984 inches. The end of theferrule receiving bore comprises a smooth flat wall 416 perpendicular tothe transverse axis of the bore. As the ferrule is inserted into thebore, and brought into abutment with end wall 416, the wall acts as aferrule stop, limiting the insertion of the ferrule 406 into the housing400. A second bore, or optics cavity 408 which houses optical device418, is formed at the opposite end of the housing. A smaller cavity 410is formed within the optics cavity 408 and is configured to support afocusing element 412, which in the preferred embodiment comprises aspherical ball lens press fit into the lens cavity 410. Lens cavity 410and ferrule receiving bore 402 are joined by a through bore 414 whichallows focused optical radiation to pass from the ball lens 412 to theoptical waveguide 404 contained within the alignment ferrule 406. Theportion of the ferrule receiving bore 402 immediately adjacent ferrulestop 416 is precision molded such that with the alignment ferrule 404fully inserted into the ferrule receiving bore 402 and in directphysical abutment against the ferrule stop 416, the optical waveguide404 contained within the alignment ferrule 406 will be centered directlyover the through bore 414. Ball lens 412 is configured to focus thelight emitted from optical device 418 mounted at the base of housing 400to a point at the opposite end of through bore 414 corresponding to theend of optical waveguide 404, thereby coupling the optical radiationinto the waveguide.

The base of housing 400 forms an annular mounting surface 420. Asubstrate member 422 is provided for mounting the optical device 418thereon. The optical device 418 may be a TO-46 can, or some other styleoptical device, either packaged or unpackaged. A number of mountingposts 424, formed integrally with housing 400, extend from the base ofthe housing perpendicular to mounting surface 420. Correspondingalignment holes 426 are formed in substrate member 422. The posts 424and holes 426 are located such that when the housing is mounted to thesubstrate member 420, the posts extend through the mounting holes,allowing the planar surface defined by annular mounting surface 420 torest flush against the flat surface of substrate member 422. As can bebest seen in FIG. 6B, alignment holes 426 are formed having a largerdiameter than mounting posts 424. This allows substrate member 422 to bemaneuvered relative to housing 400 to facilitate alignment of theoptical device 418 with the optical elements mounted within the housing400. The optical device 418 is rigidly fixed to substrate member 422,and is aligned with the optical elements within housing 400 by movingthe substrate relative to the housing. The optical elements are activelyaligned as previously discussed in order to determine the optimumrelative position between the substrate member and housing 400 where themaximum amount of optical radiation emitted from the optical device 418is coupled into the optical waveguide 404.

Upon finding the optimum relative position between the housing 400 andsubstrate member 422, it is necessary to secure the two pieces togetherto maintain that relationship. The present invention contemplates anumber of methods for bonding the housing 400 to the substrate member422 while simultaneously maintaining the proper alignment between thevarious optical components. A first method involves reflowing theplastic posts to fill the alignment holes and forming a meniscus overthe holes that extends over a portion of the substrate member (see FIG.6B). Using this method various non-contact means of melting the postscan be employed, including a CO₂ laser, an infrared heat source or hotair, among others. A similar method involves partially reflowing thepost using the methods described, and using a rivet forming tool tocompress the semi-molten plastic at the proper temperature. The rivetforming tool helps to shape the meniscus and control the flow of moltenplastic to provide cleaner final result. The results of this process areshown in FIG. 6C. As can be seen, the mounting posts 424 completely fillthe alignment holes 426 so that the substrate member 422 cannot be movedin the X-Y direction relative to the housing 400. The menisci spreadover portions of the substrate member 422 preventing the housing andsubstrate member from being separated.

Another method contemplated involves an additive bonding process where ahot melt adhesive such as melted LCP is poured into the gaps between thealignment holes 426 and the mounting posts 424 (see FIG. 6B). Yetanother method which can be used to bond the substrate member 422 to thehousing 400 is to form the substrate member out of a molded plastic, andlaser weld the housing directly to the substrate. In any case, thebonding process secures the housing 400 to the substrate, permanentlyfixing the alignment of all of the optical components mounted therein.

An additional embodiment of the invention is shown in FIG. 7. A plastichousing 500 is shown which is identical to the plastic housing 400 ofthe previous embodiment except that there are no mounting posts formedat the base of the housing. Instead of mounting posts, an annular metalinsert 524 is press fit into the second bore, or optics cavity 508 ofhousing 500. The outer surfaces 526 of the metal insert are formed withsurface features such as a knurled pattern, threads, bumps or some otherfeature known to increase the frictional adherence of adjacent surfacesto secure the insert 524 within the housing. An annular flange 528extends around one end of the metal insert perpendicular to thelongitudinal axis thereof. With the metal insert 524 fully inserted intothe optics cavity 508, the flange 528 engages the annular mountingsurface or base 520 of housing 500. In the present embodiment, theoutside surface 530 of the insert flange 526 acts as the mountingsurface for attaching a substrate member 522. The substrate member 522is formed having a metal edge so that the substrate member can be weldedto the upper surface 530 of the annular flange 528 of metal insert 524.The substrate member itself can be formed in a number of different waysto provide a weldable metal edge. For example, the substrate member canbe a typical printed circuit board having heavy copper traces or platedmetal traces formed along the edges. The metallized edges allow the PCboard to be welded to the metal flange 528 using a fillet type weld.Another option is to provide a metal plate having clearance holes forallowing the electrical leads of the optical device to extend throughthe substrate member. Forming the substrate member of a thin metal plateallows a lap weld through the substrate member rather than a fillet weldaround the edges. Yet another option is to form the substrate member 522as a metal washer, having an outer diameter corresponding to the outerdiameter of the insert flange. In this configuration, the optical deviceis mounted to one side of the washer, with the electrical leadsextending through the aperture in the center of the washer.

However substrate member 522 is configured, an optical device such as aTO 46 can is affixed thereto. The resultant subassembly can be activelyaligned to the housing 500, and welded to the outer surface 530 of theannular insert flange 528, thereby securing the proper optical alignmentof the optical device to the optical axis of the housing 500. As analternative to welding, the metallized edges of the substrate can alsobe soldered to the annular flange 528.

The plastic housing of the previous two embodiments allows improvementsto be made to the optical package which are unavailable when the housingis formed of metal. One such improvement involves mounting the focusingelement within the plastic housing. As can be seen in FIGS. 1, 2, and 3,in the previous embodiments, special provisions must be made formounting a spherical ball lens within the housing. However, if thehousing is formed of a compliant plastic material as disclosed in theembodiments depicted in FIGS. 6 and 7, retaining features can be formedin the lens cavity to hold a ball lens in place. FIG. 8A shows a crosssection of a portion of an optical housing 600 including a lens cavity602 having such a retaining feature. In this embodiment the retainingfeature comprises protrusions 604 which extend from the cavity wall 606into the cavity itself. As seen in the plan view of the lens cavity inFIG. 8B, the protrusions 604 are arrayed around the entrance to the lenscavity 602 forming a restriction therein. The protrusions 604 are sizedsuch that a ball lens 608 can be press fit into the cavity 602. As theball lens 608 is being pressed into the cavity 602, the compliantprotrusions 604 yield to the force applied by the ball lens 608,compressing sufficiently to allow the ball lens 608 to enter the cavity602. After the ball lens passes the restriction at the entrance to thecavity, the protrusions decompress to their normal expanse, capturingthe ball lens 608 within the cavity 602. While the protrusions 604 shownin FIG. 8 are hemispherical in shape, it should be clear to thoseskilled in the art that any shaped protrusion restricting the entranceto the lens cavity will suffice to retain the ball lens 608.

Another embodiment for mounting a ball lens within a plastic opticshousing is depicted in FIG. 9. This embodiment includes a plastichousing member 900, similar to that disclosed with regard to FIGS. 6,and 7. The housing includes a first bore 902 for receiving a connectorferrule, an optics cavity 908, and a lens cavity 910 disposedtherebetween. However, rather than being formed adjacent the opticscavity as in the previous embodiment, the lens cavity of the presentembodiment is formed adjacent the ferrule receiving bore 902. A ferrulestop 916 is formed of an annular shoulder at the end of the first bore902. From the inner diameter of the ferrule stop, the bore tapers towardthe lens cavity 910. The lens cavity 910 is cylindrical, havingapproximately the same diameter as a ball lens. The end of the lenscavity 910 is adjacent the optics cavity 908, with a small aperture 914communicating therebetween. An end surface 906 of the lens cavity isrounded, conforming to the shape of the ball lens 912 to be insertedtherein. Retaining features 904 protrude around the entrance to the lenscavity in a similar fashion to that discussed with regard to FIG. 8.Again, the retaining features 904, while shown here as hemisphericalprotrusions, can take on any shape desired so long as they exertsufficient pressure against the ball lens 912 to retain the ball lenswithin the lens cavity 910. With this arrangement, the ball lens 912 maybe inserted into the housing 900 through the ferrule receiving bore. Apredetermined amount of insertion force is required to compress theretaining features, and once the ball lens 912 is past, the retainingfeatures 904 expand around the entrance to the lens cavity 910 to holdthe ball lens 912 in place. Within the lens cavity 910, the ball lens isseated against the rounded end surface 906 of the cavity. A smallportion of the round surface of the ball lens protrudes through theaperture 914 between the lens cavity 910 and the optics cavity 908,extending into the lens cavity 908.

The primary advantage of the configuration depicted in FIG. 9 is thatduring the molding process for forming the housing 900, a single corepin can be used to form the ferrule receiving bore 902 and the lenscavity 910. This ensures precise alignment of these two chambers. Thus,when precision molding techniques are used to form housing 900, and aball lens is inserted into the lens cavity 910 and a connector ferruleis inserted into the bore 902, the optical fiber within the ferrule willbe precisely aligned with the focal axis of the ball lens. Therefore,the only alignment variable will be the location of the optical deviceat the opposite end of the optics cavity.

An additional advantage to the plastic housings embodied in FIG. 6 and 7is that a split bore configuration can be incorporated with the ferrulereceiving bore. A portion of plastic housing 700 employing such afeature is shown in FIG. 10. As shown, the split bore embodimentcontemplates narrow slots 702 formed in the ferrule receiving bore 704.The slots 702 extend from the receiving end of the bore 704 toward thebase 706 of the bore near where a focusing element is mounted. The slots702 allow the walls 712 of the housing to flex as a ferrule is insertedinto the bore. Precision alignment of the ferrule is only necessary atthe base end 706 of the bore adjacent the focusing element. Theflexibility of the bore sidewalls 712 diminishes toward the end of theslots, thus as a ferrule 710 is inserted into the bore, the increasingrigidity of the sidewalls 712 gradually forces the ferrule toward theprecision alignment position at the base 706 of the bore. Thisarrangement has the advantages of simplifying the mating procedure ofthe ferrule housing, and reduces the area of precision molding necessaryto properly align an optical waveguide within the housing, therebyreducing the cost of molding the plastic housing.

An alternate split bore configuration is shown in FIG. 10A. In thisembodiment, the portion of the housing 800 which defines the bore 802contains only a single longitudinal slot 804. The outer wall of thehousing member forming the ferrule receiving bore is asymmetrical aroundthe bore. Looking at the end of the bore, it can be seen that the outerwall 806 of the housing is thickest a point opposite the singlelongitudinal slot, then gradually tapers in each angular directiontoward the slot 804. The asymmetrical nature of the housing wall 806provides a uniform centering force against a connector ferrule insertedtherein. The centering force applied against the connector ferrule helpsto align the optical fiber within the ferrule with the optical axis ofthe housing.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. For example, the presentinvention may be manufactured as a pair of optical devices or an arrayof any desired number of such components. It is, therefore, intendedthat such changes and modifications be covered by the appended claims.

What is claimed is:
 1. An optical package comprising:a substrate havingan optical device mounted thereon; a plastic housing having a bore forreceiving an optical waveguide, and an optics cavity axially alignedwith the bore, the optics cavity further including a lens cavity formedtherein between the optic cavity and the bore, the lens cavity beingconfigured to receive an independent focusing element, and the opticalcavity being configured to receive the optical device; a mounting memberassociated with the housing providing alignment maneuverability of thesubstrate relative to the housing, and providing a structure for fixedlysecuring the substrate to the housing.
 2. The optical package of claim 1wherein the mounting member comprises a separate insert at leastpartially insertable into the optics cavity.
 3. The optical package ofclaim 2 wherein the insert has a base flange providing a planar surfacefor mounting the substrate thereto.
 4. The optical package of claim 3wherein the insert is formed of metal and the substrate is formed withmetallized edges.
 5. The optical package of claim 4 wherein themetallized edges of the substrate are soldered to the base flange of themetal insert.
 6. The optical package of claim 4 wherein the metallizededges of the substrate are welded to the flange of the metal insert. 7.The optical package of claim 3 wherein the substrate member comprises ametal washer defining a center aperture.
 8. The optical package of claim3 wherein the substrate member comprises a metal plate having aplurality of clearance holes formed therein.
 9. The optical package ofclaim 1 wherein the mounting member comprises a plurality of mountingposts arranged around the optics cavity, and wherein the substratedefines a plurality of mounting holes corresponding to the mountingposts, the mounting holes having a larger cross sectional area than themounting posts.
 10. The optical package of claim 9 wherein the mountingposts are formed of a reflowable plastic and the substrate is affixed tothe housing by melting the posts into the mounting holes and forming ameniscus over each mounting hole, the menisci having a larger diameterthan their corresponding mounting holes.
 11. The optical package ofclaim 10 wherein the posts are melted using a CO₂ laser.
 12. The opticalpackage of claim 10 wherein the posts are melted by a directed jet ofsuperheated compressed air.
 13. The optical package of claim 9 whereinthe mounting posts are formed of a reflowable plastic, and the substrateis affixed to the housing by heating the posts to a semi-molten stateand a rivet forming tool is used to compress the posts into the mountingholes forming a rivet head over the mounting holes.
 14. The opticalpackage of claim 9 wherein a hot melt-epoxy is injected into themounting holes forming a bond between the substrate and the mountingposts to secure the substrate to the housing.
 15. The optical package ofclaim 1 wherein the lens cavity further comprises a retaining featurefor resiliently capturing the focusing element within the lens cavity.16. The optical package of claim 15 wherein the lens cavity defines asingle entrance, and the retaining feature comprises a plurality ofsemi-compressible protrusions arrayed around the entrance to the lenscavity.
 17. The optical package of claim 16 wherein the single entranceadjoins the bore.
 18. The optical package of claim 16 wherein the singleentrance adjoins the optics cavity.
 19. The optical package of claim 1wherein the bore comprises a split bore.
 20. The optical package ofclaim 19 wherein the first bore is partially divided by at least onelongitudinal slot extending over a portion of the axial length of thebore.
 21. The optical package of claim 1 wherein the focusing elementcomprises a spherical ball lens.
 22. The optical package of claim 1wherein the lens cavity defines a single entrance adjoining the firstbore.
 23. A method of constructing an optical package comprising thesteps of:providing a plastic housing a waveguide receiving bore at afirst end, an optics cavity at a second end, the housing including aplurality of mounting posts integrally molded with the housing anddisposed around the optics cavity, and a focusing element disposedbetween the waveguide receiving bore and optics cavity, the focusingelement and bore defining an optical axis; mounting an optical device ona substrate having a plurality of alignment holes formed thereinconfigured to receive the mounting posts; aligning the optical devicewith the optical axis; and bonding the substrate to the mounting post.24. The method of claim 23 wherein the bonding step comprises reflowingthe mounting posts into the mounting holes, and forming a meniscus overthe holes extending partially over the substrate.
 25. The method ofclaim 23 wherein the bonding step comprises partially melting themounting posts and using a rivet forming tool to compress the mountingposts so that the posts expand radially to fill the holes, and a domedrivet head is formed over the holes extending partially over thesubstrate.
 26. The method of claim 23 wherein the bonding step comprisesinjecting a hot melt epoxy into the mounting holes.
 27. A method ofconstructing an optical package comprising the steps of:providing aplastic housing having a waveguide receiving bore at a first end, anoptics cavity at a second end, the housing including a metal insert atleast partially insertable into the optics cavity, and a focusingelement disposed between the waveguide receiving bore and optics cavity,the focusing element and bore defining an optical axis; mounting anoptical device on a substrate formed with metallized edges; aligning theoptical device with the optical axis; and bonding the substrate to themetal insert.
 28. The method of claim 27 wherein the bonding stepcomprises soldering the metallized edges of the substrate to the metalinsert.
 29. The method of claim 28 wherein the bonding step compriseswelding the metallized edges of the substrate to the metal insert.